Correlations between bone mineral density and demographic, lifestyle, and biochemical variables in community-dwelling Japanese women 69 years of age and over

Introduction: A few epidemiologic studies have comprehensively attempted to identify risk factors for low bone mineral density (BMD) in elderly Asian women. The purpose of this study was to identify demographic, lifestyle, and biochemical factors correlated with BMD in elderly Japanese women 69 years of age and over. Methods: The study design was cross-sectional. The subjects were 583 ambulatory women aged 69 years and over, and their average age was 74.3 (SD 4.4) years. Predictor variables were age, reproductive history, anthropometric indices, grip strength, calcium intake, lifestyle information, and serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D ( 1,25( OH)(2)D), osteocalcin (OC), and undercarboxylated osteocalcin ucOC) values. The outcome variable was forearm BMD measured with a DTX-200 osteometer. Results: Simple linear regression analyses showed that BMD was significantly positively associated with body height, weight, body mass index, grip strength, serum albumin concentration, and "housework," and negatively associated with age, years since menopause, age at menarche, number of children, serum 1,25(OH)(2)D concentration, serum OC concentration, and ucOC concentration. The stepwise multiple regression analysis showed that weight (beta= 0.00316, SE= 0.00028, R-2= 0.180), age (beta=- 0.00321, SE= 0.00050, R-2= 0.108), log-transformed serum OC (beta=- 0.0445, SE= 0.0064, R-2= 0.053), log-transformed serum 1,25(OH)(2)D (beta= - 0.0401, SE= 0.0074, R-2= 0.050), "farmwork" (beta= 0.00904, SE= 0.00426, R-2= 0.005), and serum 25( OH) D concentration (beta= 0.000281, SE= 0.000120, R-2= 0.003) were significantly associated with BMD. Conclusion: It was concluded that body weight is a major predictor of forearm BMD among the factors measured in this study in independent Japanese women 69 years of age and over and that serum 1,25( OH) 2D concentration may be associated with cortical BMD. Maintenance of body weight is very important for maintaining BMD in this population, unless a large weight aggravates obesity-related diseases. A follow-up study is needed to confirm these findings.